Vacuum electric tube



Aug. 9, 1932. A. OLLARD ET AL VACUUM ELECTRIC TUBE Filed May 15, 1924 2 Sheets-Sheet l INVENTOR5 Eric 4/ex0flde/ O//ard Erweg? Ka o/non Ra/nsan.

; ATTORNEY Aug- 9, 1932. E. A. OLLARD ET AL VACUUM ELECTRIC TUBE Filed May 15, 1924 2 Sheets-Sheet 2 ATTORN EY Patented Aug. 9, 1932 UNITED STATES PATENT oFFIcE' ERIC ALEXANDER QLLARD, OF LONDON, AND ERNEST YEOMAN ROISINSON, OF MAN- CHESTER, ENGLAND, ASSIGNORS, BY MESNE ASSIGNMENTS, TO ASSOCIATED ELEC- TRICAL INDUSTRIES LIMITED, A. BRITISHJOINT STOCK COMPANY vacuum: anaemic TUBE Application filed May 15, 1924, Ser1a1 1T0. 713,435, and in Great Britain June 2, 1828.

This invention relates to vacuum electric tube devices and like evacuated apparatus which are in part metallic, such for example as vacuum electric discharge tubes having envelopes which are partly formed of metal and which may serve as the anodes of the devices.

According to the invention the metallicportion of such a device is produced wholly or in part by electro-deposition. It preferably consists of copper. In the preferred form it consists of a copper tube which is closed at one end and the open end thereof is fusedto a vitreous portion so as to provide a gas-tight joint. The tube is produced by the deposition of copper upon a mandrel or former which is preferably rotated at a high speed during the deposition in order to produce a dense layer of copper. For example in the preferred method the mandrel is rotated so that its surface velocity is about 1000 ft. per minute.

In carrying out the invention according to one method, a mandrel of suitable shape is first made, the exterior of which corresponds to the interior of the metallic casing to be produced. This mandrel may be made of bronze or steel. In the latter case it must first be copper plated by the usual process in a cyanide bath. Preferably,v a jet of electrolyte is directed on to the rotating mandrel during the plating. Before placing the mandrel in the plating bath, the mandrel is prepared for a non-adhesive deposite by any of the ordinary methods, such, for example, as by immersion in potassium sulphide. The copper is deposited on the mandrel from an electrolyte of acid copper sulphate until the required thickness is obtained. It is then removed from the mandrel by spinning or other suitable means; for example the mandrel may be made slightly conical to facilitate removal of the case or it may be dipped before plating in a fusible conducting material such for example as Woods metal orwax graphite mixturewhich forms a thin coating over the mandrel, which coating. will flow when the mandrel is heated to remove the copper case. In this case the mandrel must be constructed slightly smaller than the required final size. The open end of the copper tube is then sealed in any manner to a vitreous container which preferably consists of a glass tube closed at one end and provided with a re-entrant tube carrying the necessary seals for the various lead-in wires of'the device. In one method the tube is sealed direct to the vitreous container. The copper tube may be greater or smaller in diameter than the glass and may be sealed either inside or outside the glass or alternatively it may be fused into the glass. The sealing of the copper tube to the glass tube may be facilitated by the use of borax as a flux during the fusion process. It may preferably be given a feather edge since it is found that the joint is more satisfactory in this case, and it facilitates the fusion of the copper tube into the glass. This feather edge may be produced, for example by grinding or spinning down the end of the copper tube or it may be produced by drawing the mandrel up from time to time in the plating bath. The copper maybe made more homogeneous by working it, for example, by spinning it after it has been deposited.

Alternatively, the copper tube may be welded to a ring of material having a .coefficient of expansion approximately equal to that of the glass employed, which ring is then sealed into or on to the vitreous container. Such a ring may be made in a known manner, for example, ofnickel steel, which may be coated with copper or it may consist of platinum. I

Various means have been proposed for fusing the copper into intimate contact with the glass. In one method a wax or fusible metal former which is made suitably conducting is attached to the open end of the glass tube which forms the vitreous part of the container. The end of the glass tube, for example a length thereof of about 2 cm. is first coated with an. adherent deposit of gold, for example, by paintingon a solution of gold chloride and heating and so producing gold. Several such coatings of this may be ap lied, or the tube may be rolled in goldlea or a combination of both methods may be adopted and the gold then fused into the glass. The copper .case is then deposited over the former and over the end of the vitreous tube; it is then fused to the glass by heating which removes the gold by al oying it with the copper and fuses the copper direct to the glass. The case may be deposited in two stages and the fusion process may be carried out between the stages so that during the fusion process the copper deposit is relatively thin.

In alternative methods a portion of the vitreous container is first given a copper coating which is fused thereto in the manner described above. A former, which is a shape to aid in the construction of the device and which is preferably of fusible alloy or wax is then attached to the open end of the tube the surface of which is rendered conducting, and the former is brought into contact with the copper band and deposition continued in the acid co per sulphate. Thus deposition will then ta e place over the sealed-in band of copper and also over the former, and hence will beperfectly continuous over its surface. After deposition to the desired thickness the former is removed by warming. If desired the thickness of deposition may be varied by raising or lowering the mandrel in the electrolyte. In another method a thin copper tube which is closed at one end and which may be formed in the manner described in the first modification'of this invention, is placed on the open end of the glass so that this open end touches the fused-in copper band. Preferably, it may also overlap and be sprung on to this fused-in copper band and a further layer deposited over the case so formed which layer is perfectly continuous and provides a container suitable for being highly exhausted. It is desirable that the copper deposit which is sprung on to the fused-in copper band should be Very thin. It may therefore preferably be filled during the deposition process with a fusible substance in order to give it rigidity and hold it firmly on to the vitreous portion of the glass.

The copper anode or envelope produced accordin to the invention may further be coatedwith a metal such as tin to render it less porous.

In the accompanying drawings constituting a part hereof and in which like reference characters designate like parts,

.Fig. 1 is a vertical sectional view partially in elevation of a discharge tube embodying the principles of the invention, and

Fig. 2 is a sectional view showing a vac- Fig. 3 is a similar view of a modification of our invention in which the metallic anode and the glass portion of the tube wall are of approximately the same diameter.

F 'g. 4 is a similar view of a modification of our invention in which the anode is first formed as a thin metallic shell and then sealed to the exterior of the glass wall portion.

Fig. 5 is a similar view of a modification in which a thin shell is first fused to the glass and the metallic anode then forced over the metal shell and the whole structure thickened by electro-deposition.

Fig. 6 is a similar view of a modification in which the glass portion is provided with a copper surface near its edge and a fusible mandrel set in position therein so that the metallic anode may be formed by electrolytic-deposition upon the latter.

Referring to Fig. 1 of the drawings the tube therein illustrated comprises in general a copper anode 1 constructed as hereinbefore described, a cathode 2 and a vitreous envelope portion 3. The copper anode 1 is substantially cylindrical and closed at one end as shown and the other end thereof is enlarged as indicated at 4 to a diameter corresponding to that of the vitreous portion 3. The edge of the enlarged portion of the anode is made thin or wedge-shaped as indicated at 5 to faeilatate the sealing thereof to the vitreous means of tungsten or molybdenum stems 7 welded thereto at one end and at the other end brazed by means of copper into holes formed in supporting members 8 and 9. The supporting member 9 comprises a steel tube which carries the stems 7 which are attached to the outer of the cathode tubes. The supporting member 8 comprises a tube having lugs which are provided with holes which accommodate the stems 7 attached to the inner of the cathode tubes. The support 8 is carried by and insulated from the supporting member 9 by means of a steatite separator a portion of which is indicated at 10. Shields for confining the tube discharge to the interelectrode space are indicated at 11 and 12, these shields being supported from the cathode members in any convenient manner. The electrode support 9 is riveted or otherwise attached to a plurality of arms 13 which are secured to the re-entrant part 6 of the vitreous portion 3 by means of clips 14;. The re- Sealed to the vitreous partion 3 in the man ner described hereinbefore.

Instead of the end of the copper anode 1 being enlarged to the diameter of the vitreous portion 3 as illustrated in Fig. 1 it may be flared as indicated at 16 in Fig. 2 and the end of the vitreous portion 3 to which the anode is attached may be tapered as indicated at 17 in Fig. 2. Or as illustrated in Fig. 3 the anode land vitreous tube 3 may be of substantially the same diameter, one fitting within the other as illustrated in' Fig. 3 wherein the vitreous portion 3 is sealed within the end of the anode 1. Alternatively, the anode 1 may be sealed within the end of-the vitreous portion 3 or the edge of the anode 1 may be fused directly into portion. 7

Referring to Fig. 4 which illustrates a modified construction the anode 1 comprises in the edge of the vitreous the first stage a thin copper shell which may until the required be formed for example by spinning or by electrolytic deposition. Such thin shell is fused or sealed to the vitreous portion 3 of the device and after fusion further depositi on of copper is eifected to thicken the walls of the anode.

Fig. 5 illustrates the method wherein the vitreous portion 14 is provided with a comparatively thin copper surface as indicated at 18 which is fused into the vitreous material. A comparatively thin copper anode shell is then forced over the end of the vitreous portion 3 carrying the deposit 18. Final- 1 1y, further deposition of copper is effected thickness is obtained, the copper thus further deposited also providing a seal between the anode 1 and the copper coating 18, that is to say, between the anode 1 and the vitreous portion 3 of the device.

Referring to Fig. 6 which illustrates another method connecting the anode portion 1 to the vitreous portion 3 the latter is provided with a copper surface 19 at its edge in the manner described in connection with Fig. 5. A fusible mandrel the surface of which is made electrically conductive in the manner hereinbefore described is then fixed to the vitreous container and the copper anode is deposited over both the mandrel and the band of copper deposition 19. One end of the mandrel is indicated by dotted lines at 20. When the deposition is sufficiently thick the mandrel is removed by melting it as described.

In Figs 4, 5 and 6, the thickness of the copper shells 1 and the deposits 18 and 19 is exaggerated for clarity of explanation. Actu ally such shells and deposits will be-made as thin as practically possible.

Various modifications can be made without departing from the scope of the invention.

We claim as our invention 1. In the method of manufacturing vacuum electric tubes, the steps which comprise portion and over formin a. portion of the envelope adult.

vitreous material and producin a. metallic portion of the envelope by attac ing to said vitreous portion a former having a conductive surface and electrolytically depositing said metallic portion on said former rotated at high speed in an electrolyte. v

2. In the method ofmanufacturing vacuum electric tubes having a vitreous portion and a copper portion, the steps which comprise directly fusing envelope portion to the vitreous enve' ope portion and electrolytically depositing copper on the copper envelope ortion to increase the thickness of its wall;

3. In the method of manufacturing vacuum electric tubes having a vitreous ortion and'a copper portion, the steps whic comprise providing a coating of copper on that part of the vitreous envelope portion to which the metallic fusing said coating to the vitreous portion, fitting a relatively thin copper envelope portion to the vitreous portion to partially overlap the fused coating thereon, and electrolytically depositin copper over the metallic the exposed portion of the fused coating to increase the wall thickness of the copper portion and also provide a hermetic seal between the copper and vitreous portions of the envelope.

In a vacuum electric reous envelope portion, a coating of copper upon a portion thereof,

ope portion fused thereto.

5. In the method um electric tubes, the step which comprises forming a portion of the envelope from a vitreous material and producing a metallic pora tion of the envelope by attaching to said vitreous portion a former havin a conducting surface and electrolytically depositing said metallic portion on said former. I

6. In the method of manufacturing vacuum electric tubes having a vitreous portion and a metallic portion, the steps which comprise fusing a coating of copper to the vitreous portion, inserting a removable mandrel in said vitreous portion and electrolytically depositing a copper envelope portion on the removable mandrel and upon the fused copper coating.

7 In the method of manufacturing vacuum electric tubes, having an envelope comprising a vitreous portion and a metallic portion,-the steps which comprise providing a coating of copper on the vitreous portion, electrolytically depositing the copper envelope portion on a removable mandrel and upon the said coating of copper, and fusing the junction between the vitreous portion and said copper coating.

8. In the method of manufacturing vacuum electric tubes having an envelope -com prising a vitreous portion and a metallic pora thin walled co per" of manufacturing vacuenvelope portion is to be united,

tube device, a vitand a metallic envetion,-the steps which comprise providing a' coating of copper on the vitreous portion, electrolytically depositing a thin copper envelope portion on a removable mandrel and upon the said coating of copper, junction between the vitreous ortion and said copper coating and .electro ytically depositing copper upon the copper envelope and over said fused junction.

In testimony whereof, we have hereunto subscribed our names this 28th day of April 1924.

ERIC ALEXANDER OLLARD. ERNEST YEOMAN ROBINSON.

fusing the 

